1. Field of the Invention
the present invention relates to corrosion protection by means of chemically resistant materials insulating metal articles from the atmospheric factors and aggressive media; and more particularly, it relates to a process for producing a tubular polymeric anticorrosion film.
The tubular polymeric anticorrosion film produced by the process according to the present invention can be useful as a preservation packaging material for the protection of metal articles from atmospheric factors.
2. Description of the Prior Art
Known in the art is the most widespread method for the protection of metals against corrosion which resides in preservation and packing of metal articles in sealed packages made from polymeric films possessing anticorrosion properties. Most widely used in the production of tubular polymeric anticorrosion films are the methods comprising extrusion of compositions incorporating volatile or contact-type inhibitors of corrosion of metals.
Known in the art is a process for producing a tubular anticorrosion polymeric film by extrusion of a composition based on polyethylene containing powder-like volatile inhibitors - a mixture of inorganic salts of .beta.-dicyclohexylamine, .beta.-cyclohexylamonium nitrite and nitrosodicyclohexylamine.
The resulting melt is air-blown into a tube upon cooling.
The tubular film produced by this process incorporates a major portion of the corrosion inhibitor in an encapsulated form so that the inhibitor is released upon its use on both sides. This results in impaired anticorrosion properties of the film and counterproductive losses of the corrosion inhibitor.
Known in the art is a process for the manufacture of a tubular polymeric anticorrosion film comprising extrusion of a melt of polmethylene and blowing of this melt into a tube simultaneously with application of a finely-divided corrosion inhibitor onto the inside surface of the formed tube by means of compressed air (SU, A, No. 859178).
Due to insufficient diffusion of the powder of the corrosion inhibitor into the volume of the film and its low adherence to the film, the latter has but a limited time of corrosion protection. Furthermore, the range of such corrosion inhibitors is rather narrow, therefore this prior art process has not found a wide commercial application.
Known in the art is a process for the manufacture of a double-layer polymeric anticorrosion film residing in that a film from a composition based on polyethelene and volatile corrosion inhibitors is laminated, on the side preliminarily coated with an adhesive, with a usual polymeric film. The process is rather complicated, features a high labor and material intensity.
Also known in the art is a process for the production of a tubular polymeric anticorrosion film (SU, A, No. 768225) which comprises extrusion of a melt of a mixture of a thermoplastic polymer with a corrosion inhibitor in a liquid phase or with its solution in a plastifying agent in an amount exceeding the limit of compatibility with this polymer, followed by blowing the melt into a tube upon cooling.
This process also features non-productive losses of the corrosion inhibitor due to its liberation and evaporation on both sides of the tubular film. This also causes reduction of the duration of corrosion protection of metal articles ensured by such film employed for packing of the articles.